What are pubic lice?
Pubic lice are tiny insects about 1-2 mm long (smaller than the head of a match). Their medical name is Phthirus pubis and they are grey or brown in colour. Sometimes they are called crabs because their 2nd and 3rd pairs of legs have crab-like claws. These claws are used to hold tightly on to hairs. Lice are blood-sucking insects which survive by feeding on tiny amounts of your blood, which they get through your skin. Female lice lay eggs (also called nits) which are smaller than a pinhead. These eggs stick to the hairs in which the lice live. The eggs hatch into lice after 6-10 days. A female louse can lay up to 300 eggs in her lifetime of 1-3 months.
Pubic lice live in hairy areas of the body. Because they prefer thick coarse hair, pubic lice commonly affect the pubic hair. However, they may also affect body hair around the anus, underarms, beard, chest and, rarely, eyebrows and even eyelashes.
Pubic lice only affect humans. They can’t be caught from, or passed to, animals.
Note: pubic lice do not live in the hair on your head, as scalp hair tends to be softer and finer, and the lice can’t hold on to these hairs. Head lice are a different type of louse (called Pediculus humanus capitis).
How do you get pubic lice?
You need close body contact to pass pubic lice on to others. Usually pubic lice are caught by having sex with a person who already has a pubic louse infestation.
It is possible to ‘catch’ pubic lice through close nonsexual physical contact with an affected person – such as kissing someone who has lice in their beard.
Pubic lice and their eggs attach very strongly to hair, they neither simply wash or brush off, nor do they fall off. They also cannot survive without a human ‘host’ to feed from. This means that you are extremely unlikely to catch pubic lice from clothing, bed linen, shared towels or toilet seats.
What are the symptoms of pubic lice?
- The main symptom is generalised itching in the affected areas, usually in the pubic hair region. Itching may take between 1 and 3 weeks to begin after you become infected. Itching is usually worse at night, when the lice feed. It is due to a sensitivity to louse saliva.
- Itchy red ‘bumps’ on the skin, in the hair-covered areas, may appear.
- Faint blue spots may appear on the skin. This occurs where the lice have been feeding.
- Skin irritation and scratching may cause redness or a rash in affected areas.
- You may develop eye inflammation if your eyelashes are affected.
- You might notice really tiny dark brown specks in your underwear or your skin – this is lice faeces (poo).
- Some people have no symptoms, but can still pass lice on to others without realising.
What is the treatment for pubic lice?
Pubic lice infestation is treated with insecticide specially formulated to be used on the human body. It kills the pubic lice. The whole body should be treated, twice – seven days apart. You should avoid getting insecticides in the eyes.
The two commonly used insecticides to treat pubic lice are malathion 0.5% aqueous lotion (Derbac-M®) and permethrin 5% dermal cream (Lyclear® Dermal Cream). Aqueous (water-based) products are preferred over alcohol-based treatments (which may cause even more skin irritation). They are easy to apply and normally work well if used properly. The following is a general guide, giving tips for success:
- Malathion is suitable for all people.
- Permethrin is NOT usually used if you are under 18, or if you are pregnant or breast-feeding (unless malathion has been tried first and not worked).
- You should apply the lotion or cream to all your body, including the scalp. This is because the lice can spread and affect many parts of your body and sometimes even the scalp. You should pay particular attention to hairy parts of your body, especially to pubic hair, hair around your anus, beards, moustaches and eyebrows. Note: this advice is based on national guidelines and may be different to what is said on the insecticide packet. The packet may say only apply from the neck down – but experts recommend that the whole body be treated (taking care to avoid getting the insecticide in the eyes).
- An average adult needs about 100 ml of lotion or 20-30 g of cream to apply to the whole body.
- Apply lotion or cream to cool, dry skin. If you have a hot bath or shower, wait until the skin cools down and is fully dry before applying.
- You should leave the lotion or cream on for the full recommended time, and then wash off. Malathion should be left on for 12 hours (overnight) and then washed off. Permethrin 5% dermal cream should be left on for 24 hours and then washed off.
- If you wash any part of your body during the treatment period, you should reapply the lotion or cream again to the washed areas.
- You do not need to shave the affected areas. The lotion or cream will clear the lice.
- Some people advise washing bed linen, towels, and clothes (particularly underwear) which has been used since a week before symptoms started. There is no good evidence that this is necessary, but some people prefer to do it.
- If your eyelashes are affected, ask a doctor for advice on how to treat these areas. Simple eye ointment or Lacri-Lube® ointment is greasy, like Vaseline® and often applied to the eyelashes with cotton buds to suffocate the lice.
- Tell your doctor or pharmacist if you are pregnant or breast-feeding as some treatments may not be suitable.
Reapply the same treatment after seven days. Although lice are usually killed by one application, not all eggs may be. The second application makes sure that any lice that hatch from eggs that survived the first application will be killed before they are old enough to lay further eggs. Note: this advice is based on national guidelines and may be different to what is said on the insecticide packet. The packet may say that one application is sufficient – but experts recommend the two applications, seven days apart.
Do family and friends need treatment?
Recent close contacts and sexual partners within the past three months should be examined for lice, and treated if infected. Remember, you can have pubic lice without symptoms.
Some other points about pubic lice
- Itching often takes a few days to settle after successful treatment.
- Consult a doctor if symptoms persist after the second application of lotion or cream. This is because pubic lice sometimes become resistant to one type of insecticide and a different insecticide may be needed.
- Avoid close body contact with others until you finish the second treatment application.
- If you got pubic lice from a sexual contact then you should be tested for other sexually transmitted infections (STIs). Your doctor may do this or refer you to a genitourinary medicine (GUM) clinic.
Further help and information
Your local GUM clinic
If you suspect that you have pubic lice or any other STI, then see your GP or contact your local GUM clinic. You can go to the local GUM clinic without a referral from your GP. You can ring the local hospital and ask for the details of the nearest clinic. It may also be listed in the phone book under ‘Genito-urinary Medicine’.
Sexual Health Information Line
Helpline: 0800 567 123 Textphone: 0800 521 361
Provides information on all aspects of STIs including contact details for GUM clinics.
Family Planning Association (FPA)
Helpline: 0845 310 1334 Web: www.fpa.org.uk
Provides information and advice on all aspects of contraception and sexual health.
British Association for Sexual Health and HIV (BASHH)
BASHH is a professional association but their website includes contact details of GUM clinics.
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